In vitro diagnostics (IVD) allows labs to assist in the diagnosis of disease based on assays performed on patient fluid samples. IVD includes various types of analytical tests and assays related to patient diagnosis and therapy that can be performed by analysis of a liquid sample taken from a patient's bodily fluids, or abscesses. These assays are typically conducted with automated clinical chemistry analyzers (analyzers) into which tubes or vials containing patient samples have been loaded.
IVD systems that process a large number of test tubes (both analyzers and automation equipment) require test tube racks that enable high-density transport and storage. Generally these tubes have barcode identifiers in the form of stickers on the outside of the tube. These barcodes are used to identify samples, allowing humans and automation systems to determine how to process sample tubes. To read these barcodes, typically an optical barcode reader/scanner is used. However, a barcode reader requires line-of-sight access to a large portion of the surface of a tube in order to read it, meaning that typically tubes must be physically removed from racks or storage trays. One alternative may include a rack that allows all of its tubes to be read in situ, via openings in the structure of the tube holders. These racks require that every tube to sit on an exterior edge, limiting the rack to a low-density one or two row design.
If a rack does not support in situ barcode reads, then each tube must be mechanically removed from the rack and transported to a barcode reader at some point in the process. If the tube is immediately processed after the barcode is read, then the cycle time impact is minimized, but a first-in-first-out (FIFO) scheduling algorithm is imposed on the overall system which may negatively impact throughput and resource utilization. If the tube is returned to the rack after its barcode is read, then a non-FIFO scheduling algorithm can be used, but the cycle time impact will be much larger. Therefore, there exist competing requirements for high-density racks, low cycle time impact, and look-ahead scheduling, which are not satisfactorily met in the existing art.
For both analyzers and automation equipment, there is a need to process a large number of test tubes. To save space in the lab, it is typically ideal to have high density tube storage for loading and unloading the tubes. However, once trays grow beyond a simple one-dimensional tube holder, tube tray, or tube rack, the barcodes become blocked within these storage apparatus. There may be no line of sight to tube labels from the outside of the tray because the interior rows of the tray are blocked by the exterior rows of the tray.
If the tray is such that it does not allow an in situ barcode reading, then there are currently a couple different solutions. One is that when an operator or sample handler singulates the tubes (i.e., when tubes are individually removed from the tray), a fixed scanner can read the barcode before the tubes are placed back in the tray. The location of the tube can be associated with the tube. This allows for random access scheduling and random access processing of the tubes, but it adds an extra processing step (e.g., a barcode reading step) to the process, and this reduces throughput and overall efficiency. Another way is that tubes can be singulated directly to the processing station, allowing that station to discover the tube's identity at the processing station. This imposes a first-in, first-out (FIFO) processing order, which prevents various efficient algorithms and other optimizations, but does not require any extra tube transfer cycle time for a dedicated barcode reading step.
Past systems have made different tradeoffs. For example, systems using high-density racks (50 tubes) and look-ahead scheduling may devote more than 20% of its cycle time to barcode reading. Systems using high-density racks that have a low cycle time impact generally process tubes using a FIFO scheduling algorithm. Most of the analyzers have low cycle time impact and look-ahead scheduling, but low-density racks (e.g., a one dimensional rack might hold five tubes).